The 32 locations are selected as these are the only ones on the public database with consistent historic weather records from around 1900 to 2000 and/or 2010. Some location records precede 1900 and some begin just after 1900.

Some locations have seen their temperature recording stations moved since 1900, often from the town post office to a nearby airport. These locational changes may affect temperature readings.

Aerial photographs are linked below so you can see the changes in location.

Average mean minimum and maximum temperatures are calculated from March 2014 to February 2015, the most recent 12 month timeframe. Albeit accurate, this recent 12 month data for each location should be considered statistically unreliable due to its brevity compared with "climate normals" that have typical year-to-year weather variations smoothed over standard periods (commonly 30 years).

This page is designed to provide a simple, convenient tool for people to observe temperature trends since weather records began in Western Australia, particularly in the context of perceived climate change.

The state of Western Australia covers 2,532,400 square kilometres and was proclaimed a British colony in 1829. The eastern border is 1,862 kilometres long and there is 12,889 kilometres of coastline. The highest elevation is Mt Meharry at 1,249 metres (4,098 feet). Western Australia had a population of 2.2 million in 2009, an increase of 17% since 2000.

Western Australia's capital of Perth is said to be on the coalface of global climate change, with 2007 Australian of the Year and Climate Change Commission chairman Tim Flannery predicting in 2004 that it may become the first city in the world to become a ghost metropolis due to lack of water (BBC, Sydney Morning Herald).

It should be noted that city and large town temperature readings may be influened by urban heat islands.

Also, it is difficult to compare all locations in Western Australia without accounting for temperatures in coastal cities and towns that are strongly influenced by ocean proximity. Overnight minima in coastal locations are several degrees warmer than inland locations because of the thermal blanket created by the ocean, and strong sea breezes reduce daytime temperatures along much of Western Australia's coastline during early-mid summer.

These natural variables have little impact on inland temperatures and this may influence comparative locational analysis.

About 83% of Western Australia's total population live in the 15 coastal cities and towns with temperatures recorded by the Australian Bureau of Meteorology since the year 1900.

The five coastal locations in Western Australia with populations above 20,000 (Albany, Bunbury, Busselton, Geraldton, Perth) have been major and expanding urban centres since colonial settlement in the early 19th century. Not surprisingly, the capital city of Perth (population 1.6 million in 2009) had the highest averaged increase in mean maximum temperature among all 32 locations, including pre-1910 data, over the hundred years (1.7 degrees C). However, it should be noted that changes in temperature recording location from Mt Eliza near the central city to the northern suburb of Mt Lawley mean Perth only has a reliable history beginning in 1994.

A temperature history comparison between the five large coastal centres and all other surveyed coastal locations suggests that the heat sink created by population and social infrastructure adds between .5 and 1 degree C to daytime maximum temperatures.

Average mean minimum in 5 locations combined has risen .81 degrees C from early to late 20th century

Average mean minimum in 5 locations combined has risen .75 degrees C from early 1900s to 2014

Note: Minima are affected by relocation of temperature ground stations in all five large coastal locations during the 20th century, with consequent falls in recorded overnight minima due to greater distance from the ocean and removal of the urban heat influence. Check all five locations below (except Busselton) to confirm significant falls in minima coinciding with ground station relocations (Albany, Bunbury, Busselton, Geraldton, Perth).

Alternatively, the five major towns and cities can be compared with all 27 coastal and inland locations over 100 years.

As well as coastal vs inland natural variables, this comparison should create an upward bias on averages because all five towns and cities excluded from the 27 locations are in the coastal southern half of Western Australia, which is much cooler than the northern half and/or inland throughout the year.

Average mean minimum in 27 locations combined has risen .65 degrees C from early to late 20th century - compared to a rise of .56 degrees C for all 32 locations including Albany, Bunbury, Busselton, Geraldton, Perth (these five locations alone increased .68 degrees C).

Average mean maximum in 27 locations combined has risen .36 degrees C from early to late 20th century - compared to a rise of .52 degrees C for all 32 locations including Albany, Bunbury, Busselton, Geraldton, Perth (these five locations alone increased 0.56 degrees C).

For 26 locations in Western Australia, the Bureau of Meteorology provides "high quality" annual data since 1910.

The bureau states that weather recordings prior to 1910 are unreliable for comparison. Regulated recording methods were introduced as of 1910 and the data the bureau supplies has been homogenized and corrected to account for artificial factors such as changes in site location, exposure, instrumentation or observation procedures (... more).

Twenty of these locations are among the 32 surveyed by this web page and their annual temperature data files (1910-2010) are linked below, including averaged 30 year temperatures from 1910 to 1939 and from 1980 to 2009, plus charts of min/mean/max temperatures since 1910:

Comparing 1979-1989 with 1999-2009, the average mean temperature across all 26 "high quality" locations increased by 0.197C over the 31 year period. Comparing 1990-1999 with 2000-2009, the average mean temperature across all 26 "high quality" locations fell by 0.0006C.

Although the pre-1910 temperature recordings in each location examined below are considered by the Bureau of Meteorology to be unreliable compared to the regulated post-1910 data, it is still worth comparing these earliest temperatures with the most recent "corrected" data from 1979-2008 in the 20 locations.

Minima

For all 20 locations, the average mean minimum rose .44 degrees C from ~1900 to 1979-2008

For 10 coastal locations, the average mean minimum rose .29 degrees C from ~1900 to 1979-2008

For 10 inland locations, the average mean minimum rose .58 degrees C from ~1900 to 1979-2008

Maxima

For all 20 locations, the average mean maximum rose .48 degrees C from ~1900 to 1979-2008

For 10 coastal locations, the average mean maximum rose .86 degrees C from ~1900 to 1979-2008

For 10 inland locations, the average mean maximum rose .10 degrees C from ~1900 to 1979-2008

The West Australian colony's earliest known meteorological analysis is The Climate of Western Australia 1876-1899(PDF 25.4mb) compiled in 1901 by then Government Astronomer William Ernest Cooke. This document contains raw, unregulated data that is considered unreliable.

As the Government Astronomer explains in this historic document: "... it may be safely assumed that the results in this document give a close approximation to the truth; sufficiently so for all practical purposes, but scarcely to be considered quite accurate enough for the scientist."

Nevertheless, this compilation contains the only known official climate records for the Western Australia colony before 1900 and although recording discrepancies may have been common, these mistakes might either inflate or deflate the real temperatures (e.g. thermometers near warm buildings or in cool locations, although a common error was heat radiation from the ground).

Combined, these 13 pre-1900 minima average 13.5 degrees C. Combining the same locations among the Bureau's quality controlled sites from 1979 to 2008, the average minimum is .37 degrees C warmer than 1876-1899 at 13.87 degrees C.

Combining the same 13 locations from March 2014 to February 2015, the average minimum is 1.20 degrees C warmer than 1876-1899 at 14.67 degrees C.

Combined, these 13 pre-1900 maxima average 24.80 degrees C. Combining the same locations among the Bureau's quality controlled sites from 1979 to 2008, the average maximum is .34 degrees C warmer than 1876-1899 at 25.14 degrees C.

Combining the same 13 locations from March 2014 to February 2015, the average maximum is 1.37 degrees C warmer than 1876-1899 at 26.16 degrees C.